1. Field of the Invention
The present invention relates to a key top, a key top lighting device, and an electronic apparatus with improved operability for use in the dark.
2. Description of the Related Art
In general, portable electronic apparatuses such as a laptop type personal computer (referred to as laptop PC hereinafter) are carried around to be used in various places. Thus, on some occasions, these types of portable electronic apparatuses are used in dark places. For example, the portable electronic apparatus may be used inside an aircraft during lights-out time, or the electronic apparatus may be used to control an OHP (overhead projector) during a conference and the like.
In such cases, the keyboard used for operating the electronic apparatus needs to be lit. However, when the keyboard is brightly lit during lights-out time in an aircraft, this light may disturb other passengers on board who are sleeping. Also, since the OHP (overhead projector) is used in a dark room in order to realize a clear projection, a bright light illuminating the keyboard may degrade the projection of the OHP.
In response to the above-mentioned problems, a switch having a configuration in which the key top itself lights up is provided (e.g. see Japanese Laid-Open Patent Application No. 10-92258). This type of switch is often used in the push buttons of cell phones and the like. Also, in this type of switch, a transparent portion through which light penetrates is provided at the key top and a light emitting element such as a light bulb or a light emitting diode facing opposite to the transparent portion is provided as well.
Thus, the light emitting elements are lit when the key tops are being operated so that the portable electronic apparatus can be used in the dark. Also, the light from the light emitting element illuminates only the key top and does not go very far beyond the periphery of the key top so that no one will be disturbed by this light.
However, in the above-described key top lighting device, basically, one light emitting element is needed for each key top. Although it is possible to light a plurality of key tops using one light emitting element, the maximum number of key tops that can be lit by one light emitting element is around four key tops. Thus, in an electronic apparatus such as the lap top PC where over 100 key tops are implemented, a large number of light emitting elements will be needed, thereby significantly raising manufacturing costs. Also, since the light emitting elements require electrical power, there will be an increase in the electric power consumption, thereby speeding up the battery energy consumption of the portable electronic apparatus.